1. Field of the Invention
The invention relates to an anti-glare protection device and, more particularly, toward an anti-glare protection device that is used on a pair of welding goggles, a welding mask, or a welding helmet and comprises a supporting part with a sight opening, a protective plate covering the sight opening, and an optical filter element arranged behind the protective plate.
2. Description of Related Art
A supporting part of welding goggles, welding masks or welding helmets, apart from its supporting function, serves to protect the welder against mechanical influences and against heat radiation. This supporting part usually consists of a plastic material, for example, of poly-carbonate and is manufactured by injection molding or by press molding.
The filter element is arranged in the sight opening of the supporting part and serves as optical protection for the wearer and, therefore, represents the actual anti-glare protection of the device. The filter element may be passive, i.e. it for example may consist of Wood's glass. The filter element, however, may also be active such that it blocks or reduces the passage of light when the external light intensity exceeds a predefined threshold value. An opto-electronic element in the form of at least one liquid-crystal cell (liquid-crystal cell or LC-cell) may be serving as active filter element. An optical sensor for detecting the external light intensity is also installed in the sight opening. Suitable means are provided for processing the measuring signal of the sensor into control signals for controlling the optical transmittance of the filter element.
The protective plate covers the sight opening of the supporting part such that the filter element and, if so required, the optical sensor are positioned behind the protective plate, i.e., when worn between the protective plate and the eyes of the welder. The protective element is transparent and it serves to protect the optical filter element from soiling and damage. The protective plate advantageously consists of a plastic material such as poly-carbonate, and is mounted on the supporting part in either a fixed or interchangeable manner. For this mounting, the supporting part and/or the protective plate are usually equipped with connecting means such that the protective plate can be installed by, for example, snapping-in and such that, when installed, is more or less pressed against the supporting part or is tensioned together with it.
It becomes manifest that filter elements and sensors necessary for active filter elements of anti-glare protection devices, even if they are protected towards the outside by the protective plate, get contaminated with dirt relatively quickly and consequently lose their functional security. It also becomes manifest that an additional protection of the wearer against smoke and gases generated during welding would be desirable.